The objectives of the proposed research are to determine precisely the nutrient requirements of normal and malignant cells derived from similar tissues in the same species, and to catalog the differences that are found. Initial emphasis is being given to development of improved media for clonal growth of normal diploid mouse cells and to definition of the exact nutrient requirements for such growth. At the present time, the cells can be grown in a synthetic medium supplemented with a mixture of dialyzed horse serum and dialyzed fetal bovine serum. During the coming year, the concentrations of all components of the synthetic portion of the medium will be adjusted to experimentally determine optimum values. In addition, the dialyzed sera will be fractionated and the nature of the growth-promoting material will be studied. As soon as the requirements of normal cells are reasonably well understood, malignant cells will be tested in similar media and any differences in nutrient responses that are detected will be studied in detail. In addition to providing improved media for clonal growth of normal and malignant mouse cells, the research program will identify any differences in nutrient requirements that may exist. Hopefully such differences can be utilized to advantage in the design of cancer therapy programs.